Before flying out from Cardiff at the weekend, he completed his preparation back in his homeland after his final home game for the Barbarians.
His trainer, Steve Raikes, told walesonline.co.uk, "He finished international rugby on Saturday and was back in the gym on Tuesday! I couldn't quite believe it when he got a text on Monday saying, " can he come in and use the gym?
"I was quite surprised it was so soon after, but that's what Leigh is like; he's very meticulous in his preparation and commitment.
"He's committed to [the] Crusaders, so he was always going to do the best he can to get out there in peak condition.
"There are levels to training and watching people perform, the way they move and when you get someone who has played as a professional for most of their working career, you can see the difference."
Raikes was most impressed with Halfpenny's attention to detail.
"He's got his Crusaders' strength plan that he has to follow in the gym. He will do everything down on the programme. Anything it said to do, he did.
"It didn't matter; there was no coach, no teammates watching him. He was just on one side of the gym doing his own thing and did every last part of his training sessions.
"He's so down to earth, people keep saying it but he is. He's very modest and a genuine person. He was a very interesting person, lots of good insights and good stories with his rugby journey and life journey."
